Polishing composition

ABSTRACT

The present invention provides a polishing composition containing an organic nitrogen-containing compound, an organic polybasic acid, an abrasive, and water, wherein the organic nitrogen-containing compound has in the molecule two or more amino groups, two or more imino groups, or one or more amino groups and one or more imino groups; a method for manufacturing a substrate with the polishing composition; and a method for reducing surface stains of a substrate with the polishing composition. The polishing composition can be suitably used, for example, in the manufacturing step for a substrate for a hard disk such as a memory hard disk.

This Application is a Divisional of co-pending U.S. application Ser. No.11/288,294, which was filed Nov. 29, 2005, which claims priority toJapanese application JP2004-347212 filed in Japan on Nov. 30, 2004, thecontent of which is hereby incorporated by reference into thisapplication.

FIELD OF THE INVENTION

The present invention relates to a polishing composition, a method formanufacturing a substrate with the polishing composition, and a methodfor reducing surface stains on a substrate with the polishingcomposition.

BACKGROUND OF THE INVENTION

In recent years, in order to progress in minimizing a unit recordingarea and increasing storage capacity, hard disks are demanded to have asmaller flying height of a magnetic head or be prevented from surfacedefects such as surface stains.

Therefore, conventionally, as disclosed in JP2002-164307 A, studies havebeen made on a polishing composition that enables smoother polishing ofthe surface of a substrate for a hard disk and that less likely causessurface defects. In addition, recently, in order to obtain a substratehaving a desired surface quality in a given time period, studies havebeen made on the use of two or more stages of polishing steps.

When abrasive grains used in a first-stage polishing step and polishingdebris remain on a substrate for a hard disk obtained in the first-stagepolishing step, the majority of these abrasive grains and polishingdebris are removed in the second-stage polishing step. However, thosethat undesirably remain unremoved lead to cause defects. Also, althoughthe residual abrasive grains and polishing debris in the first stage areindeed removed in the second-stage polishing step, they have undesirablydisadvantageous influences on the second-stage polishing step, leadingto generate scratches or pits on the substrate. In addition, thoseresidual abrasive grains and polishing debris are even more undesirablein a case where the polishing is carried out only in a single stage, ora case where the polishing is carried out in a finishing step.

In order to solve these disadvantages, it is important that the abrasivegrains and the polishing debris are removed from the substrate at thetermination of each stage of the polishing step. However, the studies ona polishing composition that gives a substrate having reduced surfacestains have been hardly conducted, so that a technique of satisfactorilysolving the disadvantage has not so far been known.

SUMMARY OF THE INVENTION

The present invention relates to:

[1] a polishing composition containing an organic nitrogen-containingcompound, an organic polybasic acid, an abrasive, and water, wherein theorganic nitrogen-containing compound has in the molecule two or moreamino groups, two or more imino groups, or one or more amino groups andone or more imino groups;[2] a method for manufacturing a substrate, including the step offeeding the polishing composition as defined in the above [α] to asubstrate to be polished at a flow rate of from 0.01 to 0.5 mL/minuteper 1 cm² of the substrate, and polishing the substrate with a polishingpad; and[3] a method for reducing surface stains on a substrate, including thestep of feeding the polishing composition as defined in the above [1] toa substrate to be polished at a flow rate of from 0.01 to 0.5 mL/minuteper 1 cm² of the substrate, and polishing the substrate with a polishingpad.

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates to a polishing composition giving fewerresidual abrasive grains and polishing debris generated by polishing ona polished substrate after polishing, higher polishing rates, and beingcapable of maintaining smoothness of the substrate; a method formanufacturing a substrate with the polishing composition; and a methodfor reducing surface stains on a substrate with the polishingcomposition.

Since the polishing composition of the present invention is used, theeffects that a substrate having excellent surface smoothness, includingfewer surface defects such as surface stains, smaller waviness, or thelike, can be efficiently manufactured are exhibited.

These and other advantages of the present invention will be apparentfrom the following description.

The feature of the polishing composition of the present invention, asmentioned above, resides in that the polishing composition contains anorganic nitrogen-containing compound, an organic polybasic acid, anabrasive, and water, wherein the organic nitrogen-containing compoundhas in the molecule two or more amino groups, two or more imino groups,or one or more amino groups and one or more imino groups. Since thepolishing composition has the above feature, the effects that asubstrate having excellent surface smoothness, including fewer surfacedefects such as surface stains, smaller waviness, or the like, can beefficiently manufactured are exhibited.

Here, the function mechanism in which the abrasive grains and polishingdebris are prevented from remaining by the polishing composition of thepresent invention is yet unknown. Although not wanting to be limited bytheory, the function is considered to be exhibited due to a synergisticeffect of a combined use of a specified organic nitrogen-containingcompound and an organic polybasic acid as explained below.

Also, while the function mechanism is yet unknown, it is deduced that anorganic polybasic acid is adsorbed to the abrasive grains and thepolishing debris, so that their surfaces are charged negatively andlikely to deposit on the substrate, and an organic nitrogen-containingcompound is adsorbed to the surfaces of abrasive grains and polishingdebris adsorbed by the organic polybasic acid to electricallyneutralize, thereby suppressing them to deposit or remain on thesubstrate.

The organic nitrogen-containing compound used in the present inventionrefers to a compound having a total of two or more groups selected froman amino group and an imino group in the molecule. Specifically, theorganic nitrogen-containing compound used in the present invention hasin the molecule two or more amino groups, two or more imino groups, orone or more amino groups and one or more imino groups. The total numberof the amino groups and the imino groups in the molecule is notparticularly limited. The total number of the amino groups and the iminogroups in the molecule is preferably from 2 to 2000, more preferablyfrom 2 to 1000, even more preferably from 2 to 200, and even morepreferably from 2 to 50, from the viewpoint of increasing polishing rateand preventing surface stains on a substrate. Specific examples thereofinclude polyalkyleneimines, diethylenetriamine, triethylenetetramine,tetraethylenepentamine, bis(3-aminopropyl)amine, 1,3-propanediamine andthe like.

Representative examples of the polyalkyleneimine includepolyethyleneimine, polypropyleneimine, polybutadieneimine and the like,including those having a linear or branched structure, or those having acyclic structure. Among them, the polyethyleneimine is preferable, fromthe viewpoint of increasing polishing rate and preventing surface stainson a substrate. The polyalkyleneimine has a molecular weight ofpreferably from 150 to 100000, more preferably from 200 to 30000, evenmore preferably from 200 to 10000, and even more preferably from 300 to2000, from the viewpoint of increasing polishing rate and reducingsurface stains on a substrate. The above-mentioned molecular weight canbe determined as a number-average molecular weight according toebulioscopy or viscosity method.

In addition, the organic nitrogen-containing compound is contained in anamount of preferably from 0.001 to 0.5% by weight, more preferably from0.001 to 0.3% by weight, and even more preferably from 0.001 to 0.1% byweight, of the polishing composition, from the viewpoint of increasingpolishing rate and preventing surface stains on a substrate.

The organic polybasic acid used in the present invention is preferably asulfur-containing organic acid, a carboxylic acid, and aphosphorus-containing organic acid. Specific examples of the organicpolybasic acid include organic sulfonic acids such as methanedisulfonicacid, ethanedisulfonic acid, phenoldisulfonic acid, andnaphthalenedisulfonic acid; polycarboxylic acids such as oxalic acid,succinic acid, glutaric acid, adipic acid, maleic acid, fumaric acid,itaconic acid, malic acid, tartaric acid, citric acid, isocitric acid,phthalic acid, nitrilotriacetic acid, and ethylenediaminetetraaceticacid; phosphorus-containing organic acids such ashydroxyethylidene-1,1-diphosphonic acid, phosphonobutanetricarboxylicacid, and ethylenediaminetetramethylenephosphonic acid; and the like.Among them, succinic acid, citric acid, malic acid, tartaric acid,hydroxyethylidene-1,1-diphosphonic acid, andethylenediaminetetramethylenephosphonic acid are preferable, citricacid, malic acid, and tartaric acid are more preferable, and citric acidis even more preferable, from the viewpoint of increasing polishingrate, reducing waviness and reducing roll-off. These compounds may beused alone or in admixture of two or more kinds.

The organic polybasic acid is contained in an amount of preferably0.002% by weight or more, more preferably 0.005% by weight or more, evenmore preferably 0.007% by weight or more, and even more preferably 0.01%by weight or more, of the polishing composition, from the viewpoint ofincreasing polishing rate and reducing waviness. In addition, theorganic polybasic acid is contained in an amount of preferably 20% byweight or less, more preferably 15% by weight or less, even morepreferably 10% by weight or less, and even more preferably 5% by weightor less, of the polishing composition, from the viewpoint of surfacequality and economic advantage. In other words, the organic polybasicacid is contained in an amount of preferably from 0.002 to 20% byweight, more preferably from 0.005 to 15% by weight, even morepreferably from 0.007 to 10% by weight, and even more preferably from0.01 to 5% by weight, of the polishing composition.

In addition, in the polishing composition of the present invention, theorganic nitrogen-containing compound and the organic polybasic acidmentioned above are contained in a weight ratio, i.e. organicnitrogen-containing compound/organic polybasic acid, of preferably 1/1or less, more preferably 1/2 or less, and even more preferably 1/5 orless, from the viewpoint of increasing the polishing rate. In addition,the weight ratio is preferably 1/10000 or more, more preferably 1/1000or more, even more preferably 1/200 or more, and even more preferably1/50 or more, from the viewpoint of preventing surface stains on asubstrate. In other words, the weight ratio is preferably from 1/10000to 1/1, more preferably from 1/1000 to 1/2, even more preferably from1/500 to 1/5, even more preferably from 1/200 to 1/5, and even morepreferably from 1/50 to 1/5, from the viewpoint of increasing polishingrate and preventing surface stains on a substrate.

As the abrasive to be used in the present invention, any abrasivesgenerally employed for polishing can be used. Examples of the abrasiveinclude, for instance, metals; carbides of metals or metalloids,nitrides of metals or metalloids, oxides of metals or metalloids,borides of metals or metalloids; diamond, and the like. The metals ormetalloids include those elements belonging to the Groups 2A, 2B, 3A,3B, 4A, 4B, 5A, 6A, 7A or 8 of the Periodic Table (long period form).Specific examples of the abrasive include aluminum oxide (hereinafterreferred to as “alumina” in some cases) particles such as α-aluminaparticles and intermediate alumina particles, silicon carbide particles,diamond particles, magnesium oxide particles, zinc oxide particles,cerium oxide particles, titanium oxide particles, zirconium oxideparticles, colloidal silica particles, fumed silica particles, and thelike. Among them, α-alumina particles, intermediate alumina particles,cerium oxide particles, zirconium oxide particles, colloidal silicaparticles, fumed silica particles, and the like are preferable, andα-alumina particles, intermediate alumina particles, colloidal silicaparticles and fumed silica particles are more preferable, and α-aluminaparticles and intermediate alumina particles are even more preferable.In addition, aluminum oxide particles are preferable from the viewpointof reducing abrasive grains and polishing debris. Further, effects of aneven more increased polishing rate and reduction in waviness areobtained by a combined use of α-alumina and an intermediate alumina, ora combined use of α-alumina and colloidal silica or fumed silica.

Among the α-alumina and the intermediate alumina mentioned above, it ispreferable that the alumina has a purity of 95% or more, more preferably97% or more, and even more preferably 99% or more, from the viewpoint ofreducing waviness, reducing surface roughness, increasing polishingrate, and preventing surface defects. In addition, α-alumina ispreferable from the viewpoint of increasing polishing rate, andintermediate aluminas such as γ-alumina, δ-alumina, θ-alumina,η-alumina, and κ-alumina are preferable, from the viewpoint of surfaceproperties and reduction in waviness. Here, the intermediate aluminaused in the present invention is a generic term referring to aluminaparticles other than α-alumina particles. Specific examples thereofinclude γ-alumina, δ-alumina, θ-alumina, η-alumina, κ-alumina, andmixtures thereof. Among the intermediate aluminas, γ-alumina, δ-alumina,θ-alumina, and mixtures thereof are preferable, and γ-alumina andθ-alumina are even more preferable, from the viewpoint of increasingpolishing rate and reducing waviness.

Even more, in the case of the intermediate alumina, the intermediatealumina has a specific surface area as determined by BET method ofpreferably from 30 to 300 m²/g, and more preferably from 50 to 200 m²/g.

The primary particles of the above-mentioned abrasive have an averageparticle size of preferably from 0.001 to 2 μm, more preferably from0.005 to 0.8 μm, and even more preferably from 0.01 to 0.5 μm, from theviewpoint of increasing polishing rate and reducing waviness. Further,when the primary particles are aggregated to form secondary particles,the secondary particles have an average particle size of preferably from0.02 to 3 μm, more preferably from 0.05 to 1 μm, even more preferablyfrom 0.1 to 0.8 μm, and even more preferably from 0.1 to 0.5 μm, fromthe viewpoint of increasing polishing rate, reducing waviness, andinhibiting surface defects. The average particle size of the primaryparticles of the abrasive is obtained by subjecting the abrasive to animage analysis by observing with a scanning electron microscope in amagnification of favorably from 3000 to 30000 times, or with atransmission electron microscope in a magnification of favorably from10000 to 500000 times, and determining the particle size. In addition,the average particle size of the secondary particles can be determinedas a volume-average particle size by using a laser diffraction method.

The specific gravity of the abrasive is preferably from 1.5 to 8, andmore preferably from 1.5 to 5, from the viewpoints of dispersibility,feed ability to the polishing device and efficiency of recovery andreuse.

The abrasive is contained in an amount of preferably from 0.05 to 40% byweight, more preferably from 0.1 to 30% by weight, even more preferablyfrom 0.5 to 25% by weight, even more preferably from 1 to 20% by weight,and even more preferably from 1 to 10% by weight, of the polishingcomposition, from the viewpoint of economic advantage and increase inpolishing rate.

Water in the polishing composition of the present invention is used as amedium, and the water is contained in an amount of preferably from 55 to99% by weight, more preferably from 60 to 97% by weight, and even morepreferably from 70 to 95% by weight, of the polishing composition, fromthe viewpoint of efficiently polishing the object to be polished.

In addition, the polishing composition of the present invention cancontain other components as occasion demands.

It is preferable that an inorganic acid is used together in thepolishing composition of the present invention, from the viewpoint offurther increasing the polishing rate and reducing the waviness. Theinorganic acid is preferably nitric acid, nitrous acid, sulfuric acid,sulfurous acid and amide sulfuric acid, and sulfuric acid, sulfurousacid and amide sulfuric acid are more preferable, and sulfuric acid iseven more preferable, from the viewpoint of increasing the polishingrate. The inorganic acid is contained in an amount of preferably from0.002 to 20% by weight, more preferably from 0.005 to 15% by weight,even more preferably from 0.007 to 10% by weight, and even morepreferably from 0.01 to 5% by weight, of the polishing composition, fromthe viewpoint of polishing rate, surface quality and economic advantage.

In addition, it is preferable that the polishing composition of thepresent invention contains an oxidizing agent, from the viewpoint ofincreasing the polishing rate. The oxidizing agent is roughly classifiedinto inorganic oxidizing agents and organic oxidizing agents. As theinorganic oxidizing agent, there can be used hydrogen peroxide, aperoxide of an alkali metal or an alkaline earth metal, a peroxosulfuricacid or a salt thereof, peroxonitric acid or a salt thereof, aperoxophosphoric acid or a salt thereof, a peroxoborate, aperoxochromate, a permanganate, a halogeno-acid or a derivative thereof,a metal salt of an inorganic acid or the like. As the organic oxidizingagent, there can be used a percarboxylic acid, a peroxide, iron (III)citrate or the like. Among them, the inorganic oxidizing agent ispreferable, when an increase of the polishing rate, availability, andeasy handling, such as water-solubility are compared. Especially, inconsideration of the environmental problems, an inorganic peroxide whichdoes not contain a heavy metal is preferable. In addition, hydrogenperoxide, a peroxosulfate, a halogeno-acid or a derivative thereof aremore preferable, and hydrogen peroxide is even more preferable, from theviewpoint of preventing the stains on the surface of the substrate to bepolished. In addition, these oxidizing agents can be used alone or inadmixture of two or more kinds.

The oxidizing agent is contained in an amount of preferably from 0.002to 20% by weight, more preferably from 0.005 to 15% by weight, even morepreferably from 0.007 to 10% by weight, and even more preferably from0.01 to 5% by weight, of the polishing composition, from the viewpointof increase in polishing rate, reduction in waviness, surface quality,and economic advantage.

In addition, other components for the polishing composition includecelluloses such as cellulose, carboxymethyl cellulose, and hydroxyethylcellulose; water-soluble alcohols such as ethanol, propanol, andethylene glycol; and the like, and also include surfactants such asalkylbenzenesulfonates, formalin condensates of naphthalenesulfonicacid, polyacrylates, and ligninsulfonates; water-soluble polymers suchas polyvinyl alcohol; and the like. These components can be used aloneor in admixture of two or more kinds. The other components can be eachcontained in an amount of preferably from 0.001 to 20% by weight, morepreferably from 0.01 to 5% by weight, and even more preferably from 0.01to 2% by weight, of the polishing composition, from the viewpoint ofexhibiting each of the functions and from the viewpoint of economicadvantages.

The concentration of each component mentioned above in the polishingcomposition is a preferred concentration upon use. The concentrationupon the preparation of the polishing composition may be in aconcentration higher than those defined above. In many cases, thepolishing composition is usually prepared as a concentrate, which isdiluted upon use.

The polishing composition of the present invention can be preferablyused in polishing a substrate for a hard disk as a substrate to bepolished. The substrate for a hard disk is not particularly limited aslong as usually known ones are used, and includes, for example, asubstrate having a metal layer formed on a surface layer such as a Ni—Pplated aluminum alloy substrate, a Ni—P plated glass substrate, and analuminum disk, a substrate made of a glassy substance or a ceramicmaterial, such as a carbon disk and a glass substrate, a substratecomposed of composites of the above substances and materials, and thelike. Among them, when the polishing composition of the presentinvention is used for a substrate having a metal layer formed on asurface layer such as a Ni—P plated aluminum alloy substrate, a Ni—Pplated glass substrate, and an aluminum disk, it is preferable becausethe abrasive grains and the polishing debris can be remarkably reduced.

It is preferable that the pH of the polishing composition is properlydetermined depending upon the kinds of the substrate to be polished. Forexample, it is preferable that the pH of the polishing composition ispreferably from 1 to 12, from the viewpoint of rinsability of thesubstrate, corrosion inhibition of the processing machine, and safety ofan operator. When the main subject for a substrate to be rinsed is asubstrate having a metal layer formed on a surface layer such as a Ni—Pplated aluminum alloy substrate, a Ni—P plated glass substrate, and analuminum disk, the pH is preferably from 1 to 7, more preferably from 1to 5, even more preferably from 1 to 4, even more preferably from 2 to4, and even more preferably 2 or more and less than 3, from theviewpoint of increasing the polishing rate. The pH can be adjusted byproperly formulating an inorganic acid, an organic acid, or a saltthereof, or a basic substance such as ammonia, sodium hydroxide,potassium hydroxide, or amine as occasion demands.

In the present invention, the effects of preventing residual abrasivegrains and polishing debris by the polishing composition can beevaluated by, for example, an observation with a microscope, anobservation with a scanning electron microscope, or the like of thesurface of the substrate after polishing. Among them, in the substratefor a hard disk, the effect can be evaluated by observing an edgeportion of its inner diameter which is less likely to be cleaned offwith these equipments. In addition, the surface of the substrate afterpolishing can be further evaluated by glow discharge optical emissionspectrometry (GDOES) or the like.

By using the polishing composition of the present invention having theconstitution mentioned above, in the step of polishing in the method formanufacturing a substrate, such as a substrate for a hard disk, theresidual abrasive grains and polishing debris generated by polishing onthe substrate, in other words, surface stains are prevented, so that thesubstrate has less surface defects such as scratches and pits on itssurface, whereby a substrate having less abrasive grains and polishingdebris can be manufactured. Therefore, the present invention relates toa method for manufacturing a substrate, and a method for reducingsurface stains of a substrate.

Each of the method for manufacturing a substrate and the method forreducing surface stains of the present invention includes the step ofpolishing a substrate to be polished with the above-mentioned polishingcomposition. In this step, the substrate to be polished can be polishedby feeding the polishing composition to the polishing side of thesubstrate pressed against platens to which a porous organicpolymer-based polishing pad is attached, and moving the platens and/orthe substrate, while applying a pressure. Therefore, the presentinvention also relates to a method for polishing a substrate using theabove-mentioned polishing composition.

In the method for manufacturing a substrate and the method for reducingsurface stains of a substrate of the present invention, it is preferablethat each method includes the step of feeding the polishing compositionto a substrate at a flow rate of preferably from 0.01 to 0.5 mL/min,more preferably from 0.02 to 0.3 mL/min, even more preferably from 0.03to 0.2 mL/min, per 1 cm² of the substrate to be polished, and polishingthe substrate with a polishing pad, from the viewpoint of increase inpolishing rate and economic advantage. Therefore, an example of themethod for manufacturing a substrate or the method for reducing surfacestains of a substrate of the present invention includes a methodincluding the step of feeding the polishing composition of the presentinvention to a substrate to be polished at a flow rate of from 0.01 to0.5 mL/minute per 1 cm² of the substrate, and polishing the substratewith a polishing pad

In addition, in the method for manufacturing a substrate of the presentinvention, it is desired that the polishing pressure upon polishing thesubstrate is adjusted to a range of from 2 to 30 kPa, preferably from 2to 20 kPa, and more preferably from 4 to 15 kPa, from the viewpoint ofincreasing polishing rate and reducing waviness.

In addition, other conditions when the polishing is carried out, such askinds of polishing machine, kinds of polishing pads, polishingtemperature, and polishing rate, are not particularly limited. When aNi—P plated aluminum alloy substrate is polished with an abrasivecontaining aluminum oxide particles, the polishing rate is preferablyfrom 0.05 to 8 μm/min, more preferably from 0.1 to 6 μm/min, even morepreferably from 0.2 to 5 μm/min, and even more preferably from 0.4 to 4μm/min, from the viewpoint of productivity and operability.

The polishing composition of the present invention is especiallyeffective in the polishing step, and the polishing composition can besimilarly applied to grinding steps other than this, for example,lapping step, and the like.

EXAMPLES

The following examples further describe and demonstrate embodiments ofthe present invention. The examples are given solely for the purposes ofillustration and are not to be construed as limitations of the presentinvention.

Examples 1 to 13, Comparative Examples 1 to 5

There were mixed together given amounts of α-alumina (average particlesize of primary particles: 0.07 μm, average particle size of secondaryparticles: 0.3 μm, specific surface area: 15 m²/g, purity: 99.9%),θ-alumina (average particle size of secondary particles: 0.2 μm,specific surface area: 120 m²/g, purity: 99.9%), an organic polybasicacid, an organic nitrogen-containing compound, and other additives aslisted in Table 1, and balance ion-exchanged water, while stirring, togive a polishing composition.

1. Polishing Process

Surfaces of a Ni—P plated aluminum alloy substrate having a thickness of1.27 mm, and a diameter of 3.5 inch (95 mm) (short-wavelength waviness:3.8 nm and long-wavelength waviness: 1.6 nm, as determined by “Zygo NewView 5032”) were polished, using a double-sided processing machine underthe following setting conditions with each of the polishing compositionsobtained in the Examples and Comparative Examples, to give a polishedobject, a Ni—P plated aluminum alloy substrate usable as a substrate fora magnetic recording medium.

The setting conditions for the double-sided processing machine are asfollows.

<Setting Conditions for Double-Sided Processing Machine]

Double-sided processing machine: Model 9B, commercially available fromSPEEDFAM CO., LTD.

Processing pressure: 9.8 kPaPolishing pad: a polishing pad for a substrate for hard disk,commercially available from FUJIBORotational speed of a platen: 50 r/min.Flow rate for a polishing composition: 100 mL/min (0.076 mL/min per 1cm² of a substrate to be polished)Polishing time period: 4 min.Number of substrates introduced: 10

3. Evaluation Methods (1) Polishing Rate

Weights of each substrate before and after polishing were measured usinga device commercially available from Sartorius under the trade name ofBP-210S. Change in weight of each substrate was obtained, and an averageof the change of 10 substrates was referred to as an amount reduced, anda value obtained by dividing the amount reduced by the polishing time isreferred to as a rate of weight reduced. The rate of weight reduced isintroduced into the following equation and converted to a polishing rate(μm/min).

Rate of Weight Reduced (g/min)=[Weight Before Polishing (g)−Weight AfterPolishing (g)]/Polishing Time (min)

Polishing Rate (μm/min)=Rate of Weight Reduced (g/min)/Area of One Sideof Substrate (mm²)/Ni—P Plating Density (g/cm³)×1000000

Here, a relative value of a polishing rate (relative rate) for each ofthe Examples and Comparative Examples is shown in Table 1, assuming thatthe polishing rate of Comparative Example 1 (1.2 μm/min) takes astandard value of 1.

(2) Surface Stains

The surface of each of the substrates after polishing was observed witha scanning electron microscope S-4000 commercially available fromHitachi, Ltd. in a magnification of 10,000, and the following 5-rankevaluations were made. Here, those ranked in 1 and 2 are failures fromthe viewpoint of practical purposes.

-   -   5: no alumina residue, polishing debris or the like is observed        on the surface at all on the surface;    -   4: alumina residue, polishing debris or the like is observed but        in less amounts on the surface;    -   3: alumina residue, polishing debris or the like is observed but        in slight amounts on the surface;    -   2: alumina residue, polishing debris or the like is observed but        in large amounts on the surface; and    -   1: alumina residue, polishing debris or the like is observed but        in much amounts on the surface.

(3) Waviness

The waviness of each substrate after the polishing was determined fortwo kinds, short-wavelength waviness and long-wavelength waviness inaccordance with the following conditions. A relative value of wavinessfor each of the Examples and Comparative Examples is shown in Table 1,assuming that each waviness of Comparative Example 1 (short-wavelengthwaviness: 0.40 nm, long-wavelength waviness: 0.42 nm) takes a standardvalue of 1. The lower the numerical value, the more the waviness beingreduced.

Device: Zygo New View 5032 Object Lens: Magnification, 2.5 times,Michelson Zooming Ratio: 0.5 Remove: Cylinder Filter type: FFT FixedBand Pass Short-Wavelength Waviness: 50 to 500 μm Long-WavelengthWaviness: 0.5 to 5 mm Area: 4.33 mm × 5.77 mm

TABLE 1 Organic Organic Nitrogen- α- θ- Polybasic Acid ContainingCompound Alumina Alumina Name of (% by (% by (% by wt.) (% by wt.)Compound wt.) Name of Compound wt.) Ex. No. 1 3 2 Citric Acid 1Polyethyleneimine 0.05 Molecular Weight 300 2 3 2 Citric Acid 1Polyethyleneimine 0.003 Molecular Weight 600 3 3 2 Citric Acid 1Polyethyleneimine 0.01 Molecular Weight 600 4 3 2 Citric Acid 1Polyethyleneimine 0.05 Molecular Weight 600 5 3 2 Citric Acid 1Polyethyleneimine 0.05 Molecular Weight 2000 6 3 2 Citric Acid 1Triethylenetetramine 0.05 7 3 2 Citric Acid 1 Bis(3-aminopropyl)amine0.05 8 3 2 Citric Acid 1 1,3-Propanediamine 0.05 9 3 2 Citric Acid 1Polyethyleneimine 0.05 Molecular Weight 600 10  3 2 Citric Acid 1Polyethyleneimine 0.05 Molecular Weight 600 11  3 2 Citric Acid/ 0.5/0.5Polyethyleneimine 0.05 Succinic Molecular Weight 600 Acid 12  3 2Succinic 1 Polyethyleneimine 0.05 Acid Molecular Weight 600 13  3 2Malic Acid 1 Polyethyleneimine 0.05 Molecular Weight 600 Comp. Ex. No. 13 2 Citric Acid 1 — — 2 3 2 Citric Acid 1 — — 3 3 2 Citric Acid 1Laurylamine Acetate 0.05 4 3 2 Citric Acid 1 N-(2-Hydroxypropyl)- 0.05N,N,N- trimethylammonium formate 5 3 2 — — Polyethyleneimine 0.05Molecular Weight 600 Other Component(s) Evaluation Results Name Short-Long- of (% by Polishing Surface Wavelength Wavelength Compound wt.) pHRate Stains Waviness Waviness Ex. No. 1 Hydrogen 0.6/0.6 2 2.5 5 0.980.70 Peroxide/ Sulfuric Acid 2 Hydrogen 0.6/0.6 2 2.3 4 0.94 0.73Peroxide/ Sulfuric Acid 3 Hydrogen 0.6/0.6 2 2.2 4 0.94 0.75 Peroxide/Sulfuric Acid 4 Hydrogen 0.6/0.6 2 2.1 5 0.93 0.77 Peroxide/ SulfuricAcid 5 Hydrogen 0.6/0.6 2 1.8 4 0.93 0.80 Peroxide/ Sulfuric Acid 6Hydrogen 0.6/0.6 2 2.2 4 0.95 0.88 Peroxide/ Sulfuric Acid 7 Hydrogen0.6/0.6 2 2.2 4 0.96 0.82 Peroxide/ Sulfuric Acid 8 Hydrogen 0.6/0.6 22.2 4 0.97 0.83 Peroxide/ Sulfuric Acid 9 Polyphosphoric 0.04 2.5 1.0 50.96 1.0 Acid 10  Ammonium 0.1  2.5 1.0 4 0.97 1.0 Sulfate 11  — — 2.51.1 5 0.95 0.98 12  — — 2.5 1.1 5 1.0 0.98 13  — — 2.5 1.0 5 1.0 1.0Comp. Ex. No. 1 — — 2.5 1 1 1 1 2 Hydrogen 0.6/0.6 2 2.4 1 0.97 0.75Peroxide/ Sulfuric Acid 3 — — 2.5 0.7 2 0.95 1.2 4 — — 2.5 0.9 1 0.981.1 5 Glycolic Acid/   1/0.04 3 0.6 4 1.1 1.1 Polyphosphoric Acid

It can be seen from the above results shown in Table 1 that thepolishing compositions obtained in Examples 1 to 13 give significantlyreduced surface stains of the substrate after polishing, and are lesslikely to generate waviness on the substrate.

The polishing composition of the present invention can be suitably used,for example, in the manufacturing step for a substrate for a hard disksuch as a memory hard disk.

The present invention being thus described, it will be obvious that thesame may be varied in many ways. Such variations are not to be regardedas a departure from the spirit and scope of the invention, and all suchmodifications as would be obvious to one skilled in the art are intendedto be included within the scope of the following claims.

1. A method for manufacturing a polished substrate for a hard disk,comprising the step of: feeding a polishing composition comprising anorganic nitrogen-containing compound, an organic polybasic acid, anabrasive, and water, wherein the organic nitrogen-containing compoundhas in the molecule two or more amino groups, two or more imino groups,or one or more amino groups and one or more imino groups to a substratefor a hard disk, and polishing the substrate with a polishing pad. 2.The method according to claim 1, wherein the abrasive is an alumina. 3.The method according to claim 1, wherein the organic nitrogen-containingcompound has a molecular weight of from 150 to
 100000. 4. The methodaccording to claim 1, wherein the organic nitrogen-containing compoundis contained in an amount of from 0.001 to 0.5% by weight of thepolishing composition.
 5. The method according to claim 1, wherein theorganic nitrogen-containing compound and the organic polybasic acid arecontained in a weight ratio of the organic nitrogen-containingcompound/the organic polybasic acid of from 1/10000 to 1/1.
 6. Themethod according to claim 1, further comprising an oxidizing agent. 7.The method according to claim 1, wherein the polishing composition has apH of from 1 to
 7. 8. The method according to claim 1, wherein a flowrate of the polishing composition is from 0.01 to 0.5 mL/minute per 1cm² of the substrate.
 9. The method according to claim 1, wherein apolishing pressure is from 2 to 30 kPa.
 10. A method for manufacturing apolished substrate, comprising the steps of: feeding a polishingcomposition comprising an organic nitrogen-containing compound, anorganic polybasic acid, an abrasive, an oxidizing agent consistingessentially of hydrogen peroxide and water, wherein the organicnitrogen-containing compound is one or more members selected from thegroup consisting of polyalkyleneimines having a molecular weight of from300 to 2000, diethylenetriamine, triethylenetetramine,tetraethylenepentamine, bis(3-aminopropyl)amine, and 1,3-propanediamine,and wherein the polishing composition has a pH of from 1 to 4 to asubstrate to be polished at a flow rate of from 0.01 to 0.5 mL/minuteper 1 cm² of the substrate, and polishing the substrate with a polishingpad.
 11. The method according to claim 10, wherein a polishing pressureis from 2 to 30 kPa.
 12. A method for reducing surface stains on asubstrate for a hard disk, comprising the steps of: feeding a polishingcomposition comprising an organic nitrogen-containing compound, anorganic polybasic acid, an abrasive, and water, wherein the organicnitrogen-containing compound has in the molecule two or more aminogroups, two or more imino groups, or one or more amino groups and one ormore imino groups to a substrate for a hard disk, and polishing thesubstrate with a polishing pad.
 13. The method according to claim 12,wherein the abrasive is an alumina.
 14. The method according to claim12, wherein the organic nitrogen-containing compound has a molecularweight of from 150 to
 100000. 15. The method according to claim 12,wherein the organic nitrogen-containing compound is contained in anamount of from 0.001 to 0.5% by weight of the polishing composition. 16.The method according to claim 12, wherein the organicnitrogen-containing compound and the organic polybasic acid arecontained in a weight ratio of the organic nitrogen-containingcompound/the organic polybasic acid of from 1/10000 to 1/1.
 17. Themethod according to claim 12, further comprising an oxidizing agent. 18.The method according to claim 12, wherein the polishing composition hasa pH of from 1 to
 7. 19. The method according to claim 12, wherein aflow rate of the polishing composition is from 0.01 to 0.5 mL/minute per1 cm² of the substrate.
 20. The method according to claim 12, wherein apolishing pressure is from 2 to 30 kPa.
 21. A method for reducingsurface stains on a substrate, comprising the steps of: feeding apolishing composition comprising an organic nitrogen-containingcompound, an organic polybasic acid, an abrasive, an oxidizing agentconsisting essentially of hydrogen peroxide and water, wherein theorganic nitrogen-containing compound is one or more members selectedfrom the group consisting of polyalkyleneimines having a molecularweight of from 300 to 2000, diethylenetriamine, triethylenetetramine,tetraethylenepentamine, bis(3-aminopropyl)amine, and 1,3-propanediamine,and wherein the polishing composition has a pH of from 1 to 4 to asubstrate to be polished at a flow rate of from 0.01 to 0.5 mL/minuteper 1 cm² of the substrate, and polishing the substrate with a polishingpad.